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<h1>D</h1>

<dl>

<dt><a name="*DB"><code>*DB</code></a>
<dd>A global constant holding the external symbol <code>{1}</code>, the <code><a
href="ref.html#dbase">database</a></code> root. All transient symbols in a
database can be reached from that root. Except during debugging, any explicit
literal access to symbols in the database should be avoided, because otherwise a
memory leak might occur (The garbage collector temporarily sets <code>*DB</code>
to <code>NIL</code> and restores its value after collection, thus disposing of
all external symbols not currently used in the program).

<pre><code>
: (show *DB)
{1} NIL
   +City {P}
   +Person {3}
-> {1}
: (show '{P})
{P} NIL
   nm (566 . {AhDx})
-> {P}
: (show '{3})
{3} NIL
   tel (681376 . {Agyl})
   nm (1461322 . {2gu7})
-> {3}
</code></pre>

<dt><a name="*Dbg"><code>*Dbg</code></a>
<dd>A boolean variable indicating "debug mode". It can be conveniently switched
on with a trailing <code>+</code> command line argument (see <a
href="ref.html#invoc">Invocation</a>). When non-<code>NIL</code>, the <code><a
href="ref_.html#$">$</a></code> (tracing) and <code><a
href="ref_.html#!">!</a></code> (breakpoint) functions are enabled, and the
current line number and file name will be stored in symbol properties by
<code><a href="refD.html#de">de</a></code>, <code><a
href="refD.html#def">def</a></code> and <code><a
href="refD.html#dm">dm</a></code>. See also <code><a
href="refD.html#debug">debug</a></code>, <code><a
href="refT.html#trace">trace</a></code> and <code><a
href="refL.html#lint">lint</a></code>.

<pre><code>
: (de foo (A B) (* A B))
-> foo
: (trace 'foo)
-> foo
: (foo 3 4)
 foo : 3 4
 foo = 12
-> 12
: (let *Dbg NIL (foo 3 4))
-> 12
</code></pre>

<dt><a name="*Dbs"><code>*Dbs</code></a>
<dd>A global variable holding a list of numbers (block size scale factors, as
needed by <code><a href="refP.html#pool">pool</a></code>). It is typically set
by <code><a href="refD.html#dbs">dbs</a></code>
and <code><a href="refD.html#dbs+">dbs+</a></code>.

<pre><code>
: *Dbs
-> (1 2 1 0 2 3 3 3)
</code></pre>

<dt><a name="+Date"><code>+Date</code></a>
<dd>Class for calender dates (as calculated by <code><a
href="refD.html#date">date</a></code>), a subclass of <code><a
href="refN.html#+Number">+Number</a></code>. See also <code><a
href="ref.html#dbase">Database</a></code>.

<pre><code>
(rel dat (+Ref +Date))  # Indexed date
</code></pre>

<dt><a name="+Dep"><code>+Dep</code></a>
<dd>Prefix class for maintaining depenencies between <code><a
href="refR.html#+relation">+relation</a></code>s. Expects a list of (symbolic)
attributes that depend on this relation. Whenever this relations is cleared
(receives a value of <code>NIL</code>), the dependent relations will also be
cleared, triggering all required side-effects. See also <code><a
href="ref.html#dbase">Database</a></code>.

<p>In the following example, the index entry for the item pointing to the
position (and, therefore, to the order) is cleared in case the order is deleted,
or this position is deleted from the order:

<pre><code>
(class +Pos +Entity)                # Position class
(rel ord (+Dep +Joint)              # Order of that position
   (itm)                               # 'itm' specifies the dependency
   pos (+Ord) )                        # Arguments to '+Joint'
(rel itm (+Ref +Link) NIL (+Item))  # Item depends on the order
</code></pre>

<dt><a name="d"><code>(d) -> T</code></a>
<dd>Inserts <code><a href="ref_.html#!">!</a></code> breakpoints into all
subexpressions of the current breakpoint. Typically used when single-stepping a
function or method with <code><a href="refD.html#debug">debug</a></code>. See
also <code><a href="refU.html#u">u</a></code> and <code><a
href="refU.html#unbug">unbug</a></code>.

<pre><code>
! (d)                            # Debug subexpression(s) at breakpoint
-> T
</code></pre>

<dt><a name="daemon"><code>(daemon 'sym . prg) -> fun</code></a>
<dt><code>(daemon '(sym . cls) . prg) -> fun</code>
<dt><code>(daemon '(sym sym2 [. cls]) . prg) -> fun</code>
<dd>Inserts <code>prg</code> in the beginning of the function (first form), the
method body of <code>sym</code> in <code>cls</code> (second form) or in the
class obtained by <code><a href="refG.html#get">get</a></code>ing
<code>sym2</code> from <code><a href="refC.html#*Class">*Class</a></code> (or
<code>cls</code> if given) (third form). Built-in functions (C-function pointer)
are automatically converted to Lisp expressions. See also <code><a
href="refE.html#expr">expr</a></code>, <code><a
href="refP.html#patch">patch</a></code> and <code><a
href="refR.html#redef">redef</a></code>.

<pre><code>
: (de hello () (prinl "Hello world!"))
-> hello

: (daemon 'hello (prinl "# This is the hello world program"))
-> (NIL (prinl "# This is the hello world program") (prinl "Hello world!"))
: (hello)
# This is the hello world program
Hello world!
-> "Hello world!"

: (daemon '* (msg 'Multiplying))
-> (@ (msg 'Multiplying) (pass $134532148))
: *
-> (@ (msg 'Multiplying) (pass $134532148))
: (* 1 2 3)
Multiplying
-> 6
</code></pre>

<dt><a name="dat$"><code>(dat$ 'dat ['sym]) -> sym</code></a>
<dd>Formats a <code><a href="refD.html#date">date</a></code> <code>dat</code> in
ISO format, with an optional delimiter character <code>sym</code>. See also
<code><a href="ref_.html#$dat">$dat</a></code>, <code><a
href="refT.html#tim$">tim$</a></code>, <code><a
href="refD.html#datStr">datStr</a></code> and <code><a
href="refD.html#datSym">datSym</a></code>.

<pre><code>
: (dat$ (date))
-> "20070601"
: (dat$ (date) "-")
-> "2007-06-01"
</code></pre>

<dt><a name="datStr"><code>(datStr 'dat ['flg]) -> sym</code></a>
<dd>Formats a <code><a href="refD.html#date">date</a></code> according to the
current <code><a href="refL.html#locale">locale</a></code>. If <code>flg</code>
is non-<code>NIL</code>, the year will be formatted modulo 100. See also
<code><a href="refD.html#dat$">dat$</a></code>, <code><a
href="refD.html#datSym">datSym</a></code>, <code><a
href="refS.html#strDat">strDat</a></code>, <code><a
href="refE.html#expDat">expDat</a></code>, <code><a
href="refE.html#expTel">expTel</a></code> and <code><a
href="refD.html#day">day</a></code>.

<pre><code>
: (datStr (date))
-> "2007-06-01"
: (locale "DE" "de")
-> NIL
: (datStr (date))
-> "01.06.2007"
: (datStr (date) T)
-> "01.06.07"
</code></pre>

<dt><a name="datSym"><code>(datSym 'dat) -> sym</code></a>
<dd>Formats a <code><a href="refD.html#date">date</a></code> <code>dat</code> in
in symbolic format (DDmmmYY). See also <code><a
href="refD.html#dat$">dat$</a></code> and <code><a
href="refD.html#datStr">datStr</a></code>.

<pre><code>
: (datSym (date))
-> "01jun07"
</code></pre>

<dt><a name="date"><code>(date ['T]) -> dat</code></a>
<dt><code>(date 'dat) -> (y m d)</code>
<dt><code>(date 'y 'm 'd) -> dat | NIL</code>
<dt><code>(date '(y m d)) -> dat | NIL</code>
<dd>Calculates a (gregorian) calendar date. It is represented as a day number,
starting first of March of the year 0 AD. When called without arguments, the
current date is returned. When called with a <code>T</code> argument, the
current Coordinated Universal Time (UTC) is returned. When called with a single
number <code>dat</code>, it is taken as a date and a list with the corresponding
year, month and day is returned. When called with three numbers (or a list of
three numbers) for the year, month and day, the corresponding date is returned
(or <code>NIL</code> if they do not represent a legal date). See also <code><a
href="refT.html#time">time</a></code>, <code><a
href="refS.html#stamp">stamp</a></code>, <code><a
href="ref_.html#$dat">$dat</a></code>, <code><a
href="refD.html#dat$">dat$</a></code>, <code><a
href="refD.html#datSym">datSym</a></code>, <code><a
href="refD.html#datStr">datStr</a></code>, <code><a
href="refS.html#strDat">strDat</a></code>, <code><a
href="refE.html#expDat">expDat</a></code>, <code><a
href="refD.html#day">day</a></code>, <code><a
href="refW.html#week">week</a></code> and <code><a
href="refU.html#ultimo">ultimo</a></code>.

<pre><code>
: (date)                         # Today
-> 730589
: (date 2000 6 12)               # 12-06-2000
-> 730589
: (date 2000 22 5)               # Illegal date
-> NIL
: (date (date))                  # Today's year, month and day
-> (2000 6 12)
: (- (date) (date 2000 1 1))     # Number of days since first of January
-> 163
</code></pre>

<dt><a name="day"><code>(day 'dat ['lst]) -> sym</code></a>
<dd>Returns the name of the day for a given <code><a
href="refD.html#date">date</a></code> <code>dat</code>, in the language of the
current <code><a href="refL.html#locale">locale</a></code>. If <code>lst</code>
is given, it should be a list of alternative weekday names. See also <code><a
href="refW.html#week">week</a></code>, <code><a
href="refD.html#datStr">datStr</a></code> and <code><a
href="refS.html#strDat">strDat</a></code>.

<pre><code>
: (day (date))
-> "Friday"
: (locale "DE" "de")
-> NIL
: (day (date))
-> "Freitag"
: (day (date) '("Mo" "Tu" "We" "Th" "Fr" "Sa" "Su"))
-> "Fr"
</code></pre>

<dt><a name="db"><code>(db 'var 'cls ['hook] 'any ['var 'any ..]) -> sym | NIL</code></a>
<dd>Returns a database object of class <code>cls</code>, where the values for
the <code>var</code> arguments correspond to the <code>any</code> arguments. If
a matching object cannot be found, <code>NIL</code> is returned.
<code>var</code>, <code>cls</code> and <code>hook</code> should specify a
<code><a href="refT.html#tree">tree</a></code> for <code>cls</code> or one of
its superclasses. See also <code><a href="refA.html#aux">aux</a></code>,
<code><a href="refC.html#collect">collect</a></code>, <code><a
href="refR.html#request">request</a></code>, <code><a
href="refF.html#fetch">fetch</a></code>, <code><a
href="refI.html#init">init</a></code> and <code><a
href="refF.html#step">step</a></code>.

<pre><code>
: (db 'nr '+Item 1)
-> {3-1}
: (db 'nm '+Item "Main Part")
-> {3-1}
</code></pre>

<dt><a name="db/3"><code>db/3</code></a>
<dt><a name="db/4"><code>db/4</code></a>
<dt><a name="db/5"><code>db/5</code></a>
<dd><a href="ref.html#pilog">Pilog</a> database predicate that returns objects
matching the given key/value (and optional hook) relation. The relation should
be of type <code><a href="refI.html#+index">+index</a></code>. For the key
pattern applies:

<p><ul>
<li>a symbol (string) returns all entries which start with that string
<li>other atoms (numbers, external symbols) match as they are
<li>cons pairs constitute a range, returning objects
   <ul>
   <li>in increasing order if the CDR is greater than the CAR
   <li>in decreasing order otherwise
   </ul>
<li>other lists are matched for <code><a href="refA.html#+Aux">+Aux</a></code>
key combinations
</ul>

<p>The optional hook can be supplied as the third argument. See also <code><a
href="refS.html#select/3">select/3</a></code> and <code><a
href="refR.html#remote/2">remote/2</a></code>.

<pre><code>
: (? (db nr +Item @Item))              # No value given
 @Item={3-1}
 @Item={3-2}
 @Item={3-3}
 @Item={3-4}
 @Item={3-5}
 @Item={3-6}
-> NIL

: (? (db nr +Item 2 @Item))            # Get item no. 2
 @Item={3-2}
-> NIL

: (? (db nm +Item Spare @Item) (show @Item))  # Search for "Spare.."
{3-2} (+Item)
   pr 1250
   inv 100
   sup {2-2}
   nm "Spare Part"
   nr 2
 @Item={3-2}
-> NIL
</code></pre>

<dt><a name="db:"><code>(db: cls ..) -> num</code></a>
<dd>Returns the database file number for objects of the type given by the
<code>cls</code> argument(s). Needed, for example, for the creation of <code><a
href="refN.html#new">new</a></code> objects. See also <code><a
href="refD.html#dbs">dbs</a></code>.

<pre><code>
: (db: +Item)
-> 3
</code></pre>

<dt><a name="dbSync"><code>(dbSync) -> flg</code></a>
<dd>Starts a database transaction, by trying to obtain a <code><a
href="refL.html#lock">lock</a></code> on the database root object <code><a
href="refD.html#*DB">*DB</a></code>, and then calling <code><a
href="refS.html#sync">sync</a></code> to synchronize with possible changes from
other processes. When all desired modifications to external symbols are done,
<code>(<a href="refC.html#commit">commit</a> 'upd)</code> should be called. See
also <code><a href="ref.html#dbase">Database</a></code>.

<pre><code>
(let? Obj (rd)             # Get object?
   (dbSync)                # Yes: Start transaction
   (put> Obj 'nm (rd))     # Update
   (put> Obj 'nr (rd))
   (put> Obj 'val (rd))
   (commit 'upd) )         # Close transaction
</code></pre>

<dt><a name="dbck"><code>(dbck ['cnt] 'flg) -> any</code></a>
<dd>Performs a low-level integrity check of the current (or <code>cnt</code>'th)
database file, and returns <code>NIL</code> (or the number of blocks and symbols
if <code>flg</code> is non-<code>NIL</code>) if everything seems correct.
Otherwise, a string indicating an error is returned. As a side effect, possibly
unused blocks (as there might be when a <code><a
href="refR.html#rollback">rollback</a></code> is done before <code><a
href="refC.html#commit">commit</a></code>ing newly allocated (<code><a
href="refN.html#new">new</a></code>) external symbols) are appended to the free
list.

<pre><code>
: (pool "db")
-> T
: (dbck)
-> NIL
</code></pre>

<dt><a name="dbs"><code>(dbs . lst)</code></a>
<dd>Initializes the global variable <code><a
href="refD.html#*Dbs">*Dbs</a></code>. Each element in <code>lst</code> has a
number in its CAR (the block size scale factor of a database file, to be stored
in <code>*Dbs</code>). The CDR elements are either classes (so that objects of
that class are later stored in the corresponding file), or lists with a class in
the CARs and a list of relations in the CDRs (so that index trees for these
relations go into that file). See also <code><a
href="refD.html#dbs+">dbs+</a></code> and <code><a
href="refP.html#pool">pool</a></code>.

<pre><code>
(dbs
   (1 +Role +User +Sal)                         # (1 . 128)
   (2 +CuSu)                                    # (2 . 256)
   (1 +Item +Ord)                               # (3 . 128)
   (0 +Pos)                                     # (4 . 64)
   (2 (+Role nm) (+User nm) (+Sal nm))          # (5 . 256)
   (4 (+CuSu nr plz tel mob))                   # (6 . 1024)
   (4 (+CuSu nm))                               # (7 . 1024)
   (4 (+CuSu ort))                              # (8 . 1024)
   (4 (+Item nr sup pr))                        # (9 . 1024)
   (4 (+Item nm))                               # (10 . 1024)
   (4 (+Ord nr dat cus))                        # (11 . 1024)
   (4 (+Pos itm)) )                             # (12 . 1024)

: *Dbs
-> (1 2 1 0 2 4 4 4 4 4 4 4)
: (get '+Item 'Dbf)
-> (3 . 128)
: (get '+Item 'nr 'dbf)
-> (9 . 1024)
</code></pre>

<dt><a name="dbs+"><code>(dbs+ 'num . lst)</code></a>
<dd>Extends the list of database sizes stored in <code><a
href="refD.html#*Dbs">*Dbs</a></code>. <code>num</code> is the initial offset
into the list. See also <code><a href="refD.html#dbs">dbs</a></code>.

<pre><code>
(dbs+ 9
   (1 +NewCls)                                  # (9 . 128)
   (3 (+NewCls nr nm)) )                        # (10 . 512)
</code></pre>

<dt><a name="de"><code>(de sym . any) -> sym</code></a>
<dd>Assigns a definition to the <code>sym</code> argument, by setting its
<code>VAL</code> to the <code>any</code> argument. If the symbol has already
another value, a "redefined" message is issued. When the value of the global
variable <a href="refD.html#*Dbg">*Dbg</a> is non-<code>NIL</code>, the current
line number and file name (if any) are stored in the <code>*Dbg</code> property
of <code>sym</code>. <code>de</code> is the standard way to define a function.
See also <code><a href="refD.html#def">def</a></code>, <code><a
href="refD.html#dm">dm</a></code> and <code><a
href="refU.html#undef">undef</a></code>.

<pre><code>
: (de foo (X Y) (* X (+ X Y)))  # Define a function
-> foo
: (foo 3 4)
-> 21

: (de *Var . 123)  # Define a variable value
: *Var
-> 123
</code></pre>

<dt><a name="debug"><code>(debug 'sym) -> T</code></a>
<dt><code>(debug 'sym 'cls) -> T</code>
<dt><code>(debug '(sym . cls)) -> T</code>
<dd>Inserts a <code><a href="ref_.html#!">!</a></code> breakpoint function call
at the beginning and all top-level expressions of the function or method body of
<code>sym</code>, to allow a stepwise execution. Typing <code>(<a
href="refD.html#d">d</a>)</code> at a breakpoint will also debug the current
subexpression, and <code>(<a href="refE.html#e">e</a>)</code> will evaluate the
current subexpression. The current subexpression is stored in the global
variable <code><a href="ref_.html#^">^</a></code>. See also <code><a
href="refU.html#unbug">unbug</a></code>, <code><a
href="refD.html#*Dbg">*Dbg</a></code>, <code><a
href="refT.html#trace">trace</a></code> and <code><a
href="refL.html#lint">lint</a></code>.

<pre><code>
: (de tst (N)                    # Define tst
   (println (+ 3 N)) )
-> tst
: (debug 'tst)                   # Set breakpoints
-> T
: (pp 'tst)
(de tst (N)
   (! println (+ 3 N)) )         # Breakpoint '!'
-> tst
: (tst 7)                        # Execute
(println (+ 3 N))                # Stopped at beginning of 'tst'
! (d)                            # Debug subexpression
-> T
!                                # Continue
(+ 3 N)                          # Stopped in subexpression
! N                              # Inspect variable 'N'
-> 7
!                                # Continue
10                               # Output of print statement
-> 10                            # Done
: (unbug 'tst)
-> T
: (pp 'tst)                      # Restore to original
(de tst (N)
   (println (+ 3 N)) )
-> tst
</code></pre>

<dt><a name="dec"><code>(dec 'num) -> num</code></a>
<dt><code>(dec 'var ['num]) -> num</code>
<dd>The first form returns the value of <code>num</code> decremented by 1. The
second form decrements the <code>VAL</code> of <code>var</code> by 1, or by
<code>num</code>. If the first argument is <code>NIL</code>, it is returned
immediately. <code>(dec 'num)</code> is equivalent to <code>(- 'num 1)</code>
and <code>(dec 'var)</code> is equivalent to <code>(set 'var (- var 1))</code>.
See also <code><a href="refI.html#inc">inc</a></code> and <code><a
href="ref_.html#-">-</a></code>.

<pre><code>
: (dec -1)
-> -2
: (dec 7)
-> 6
: (setq N 7)
-> 7
: (dec 'N)
-> 6
: (dec 'N 3)
-> 3
</code></pre>

<dt><a name="def"><code>(def 'sym 'any) -> sym</code></a>
<dt><code>(def 'sym1 'sym2 'any) -> sym1</code>
<dd>The first form assigns a definition to the first <code>sym</code> argument,
by setting its <code>VAL</code>'s to <code>any</code>. The second form defines a
property value <code>any</code> for the first argument's <code>sym2</code> key.
If any of these values existed and was changed in the process, a "redefined"
message is issued. When the value of the global variable <a
href="refD.html#*Dbg">*Dbg</a> is non-<code>NIL</code>, the current line number
and file name (if any) are stored in the <code>*Dbg</code> property of
<code>sym</code>. See also <code><a href="refD.html#de">de</a></code> and
<code><a href="refD.html#dm">dm</a></code>.

<pre><code>
: (def 'b '((X Y) (* X (+ X Y))))
-> b
: (def 'b 999)
# b redefined
-> b
</code></pre>

<dt><a name="default"><code>(default var 'any ..) -> any</code></a>
<dd>Stores new values <code>any</code> in the <code>var</code> arguments only if
their current values are <code>NIL</code>. Otherwise, their values are left
unchanged. In any case, the last <code>var</code>'s value is returned.
<code>default</code> is used typically in functions to initialize optional
arguments.

<pre><code>
: (de foo (A B)               # Function with two optional arguments
   (default  A 1  B 2)        # The default values are 1 and 2
   (list A B) )
-> foo
: (foo 333 444)               # Called with two arguments
-> (333 444)
: (foo 333)                   # Called with one arguments
-> (333 2)
: (foo)                       # Called without arguments
-> (1 2)
</code></pre>

<dt><a name="del"><code>(del 'any 'var) -> lst</code></a>
<dd>Deletes <code>any</code> from the list in the value of <code>var</code>, and
returns the remaining list. <code>(del 'any 'var)</code> is equivalent to
<code>(set 'var (delete 'any var))</code>. See also <code><a
href="refD.html#delete">delete</a></code>, <code><a
href="refC.html#cut">cut</a></code> and <code><a
href="refP.html#pop">pop</a></code>.

<pre><code>
: (setq S '((a b c) (d e f)))
-> ((a b c) (d e f))
: (del '(d e f) 'S)
-> ((a b c))
: (del 'b S)
-> (a c)
</code></pre>

<dt><a name="delete"><code>(delete 'any 'lst) -> lst</code></a>
<dd>Deletes <code>any</code> from <code>lst</code>. If <code>any</code> is
contained more than once in <code>lst</code>, only the first occurrence is
deleted. See also <code><a href="refD.html#delq">delq</a></code>, <code><a
href="refR.html#remove">remove</a></code> and <code><a
href="refI.html#insert">insert</a></code>.

<pre><code>
: (delete 2 (1 2 3))
-> (1 3)
: (delete (3 4) '((1 2) (3 4) (5 6) (3 4)))
-> ((1 2) (5 6) (3 4))
</code></pre>

<dt><a name="delete/3"><code>delete/3</code></a>
<dd><a href="ref.html#pilog">Pilog</a> predicate that succeeds if deleting the
first argument from the list in the second argument is equal to the third
argument. See also <code><a href="refD.html#delete">delete</a></code> and
<code><a href="refM.html#member/2">member/2</a></code>.

<pre><code>
: (? (delete b (a b c) @X))
 @X=(a c)
-> NIL
</code></pre>

<dt><a name="delq"><code>(delq 'any 'lst) -> lst</code></a>
<dd>Deletes <code>any</code> from <code>lst</code>. If <code>any</code> is
contained more than once in <code>lst</code>, only the first occurrence is
deleted. <code><a href="ref_.html#==">==</a></code> is used for comparison
(pointer equality). See also <code><a href="refD.html#delete">delete</a></code>,
<code><a href="refA.html#asoq">asoq</a></code>, <code><a
href="refM.html#memq">memq</a></code>, <code><a
href="refM.html#mmeq">mmeq</a></code> and <a href="ref.html#cmp">Comparing</a>.

<pre><code>
: (delq 'b '(a b c))
-> (a c)
: (delq (2) (1 (2) 3))
-> (1 (2) 3)
</code></pre>

<dt><a name="dep"><code>(dep 'cls) -> cls</code></a>
<dd>Displays the "dependencies" of <code>cls</code>, i.e. the tree of
superclasses and the tree of subclasses. See also <code><a
href="ref.html#oop">OO Concepts</a></code>, <code><a
href="refC.html#class">class</a></code> and <code><a
href="refC.html#can">can</a></code>.

<pre><code>
: (dep '+Number)           # Dependencies of '+Number'
   +relation               # Single superclass is '+relation'
+Number
   +Date                   # Subclasses are '+Date' and '+Time'
   +Time
-> +Number
</code></pre>

<dt><a name="depth"><code>(depth 'lst) -> (cnt1 . cnt2)</code></a>
<dd>Returns the maximal (<code>cnt1</code>) and the average (<code>cnt2</code>)
"depth" of a tree structure as maintained by <code><a
href="refI.html#idx">idx</a></code>. See also <code><a
href="refL.html#length">length</a></code> and <code><a
href="refS.html#size">size</a></code>.

<pre><code>
: (off X)                                    # Clear variable
-> NIL
: (for N (1 2 3 4 5 6 7) (idx 'X N T))       # Build a degenerated tree
-> NIL
: X
-> (1 NIL 2 NIL 3 NIL 4 NIL 5 NIL 6 NIL 7)   # Only right branches
: (depth X)
-> (7 . 4)                                   # Depth is 7, average 4
</code></pre>

<dt><a name="diff"><code>(diff 'lst 'lst) -> lst</code></a>
<dd>Returns the difference of the <code>lst</code> arguments. See also <code><a
href="refS.html#sect">sect</a></code>.

<pre><code>
: (diff (1 2 3 4 5) (2 4))
-> (1 3 5)
: (diff (1 2 3) (1 2 3))
-> NIL
</code></pre>

<dt><a name="different/2"><code>different/2</code></a>
<dd><a href="ref.html#pilog">Pilog</a> predicate that succeeds if the two
arguments are different. See also <code><a
href="refE.html#equal/2">equal/2</a></code>.

<pre><code>
: (? (different 3 4))
-> T
</code></pre>

<dt><a name="dir"><code>(dir ['any] ['flg]) -> lst</code></a>
<dd>Returns a list of all filenames in the directory <code>any</code>. Names
starting with a dot '<code>.</code>' are ignored, unless <code>flg</code> is
non-<code>NIL</code>. See also <code><a href="refC.html#cd">cd</a></code> and
<code><a href="refI.html#info">info</a></code>.

<pre><code>
: (filter '((F) (tail '(. c) (chop F))) (dir "src/"))
-> ("main.c" "subr.c" "gc.c" "io.c" "big.c" "sym.c" "tab.c" "flow.c" ..
</code></pre>

<dt><a name="dirname"><code>(dirname 'any) -> sym</code></a>
<dd>Returns the directory part of a path name <code>any</code>. See also
<code><a href="refB.html#basename">basename</a></code> and <code><a
href="refP.html#path">path</a></code>.

<pre><code>
: (dirname "a/b/c/d")
-> "a/b/c/"
</code></pre>

<dt><a name="dm"><code>(dm sym . fun|cls2) -> sym</code></a>
<dt><code>(dm (sym . cls) . fun|cls2) -> sym</code>
<dt><code>(dm (sym sym2 [. cls]) . fun|cls2) -> sym</code>
<dd>Defines a method for the message <code>sym</code> in the current class,
implicitly given by the value of the global variable <code><a
href="refC.html#*Class">*Class</a></code>, or - in the second form - for the
explicitly given class <code>cls</code>. In the third form, the class object is
obtained by <code><a href="refG.html#get">get</a></code>ing <code>sym2</code>
from <code><a href="refC.html#*Class">*Class</a></code> (or <code>cls</code> if
given). If the method for that class existed and was changed in the process, a
"redefined" message is issued. If - instead of a method <code>fun</code> - a
symbol specifying another class <code>cls2</code> is given, the method from that
class is used (explicit inheritance). When the value of the global variable <a
href="refD.html#*Dbg">*Dbg</a> is non-<code>NIL</code>, the current line number
and file name (if any) are stored in the <code>*Dbg</code> property of
<code>sym</code>. See also <code><a href="ref.html#oop">OO Concepts</a></code>,
<code><a href="refD.html#de">de</a></code>, <code><a
href="refU.html#undef">undef</a></code>, <a href="refC.html#class">class</a>, <a
href="refR.html#rel">rel</a>, <a href="refV.html#var">var</a>, <a
href="refM.html#method">method</a>, <a href="refS.html#send">send</a> and <a
href="refT.html#try">try</a>.

<pre><code>
: (dm start> ()
   (super)
   (mapc 'start> (: fields))
   (mapc 'start> (: arrays)) )

: (dm foo> . +OtherClass)  # Explicitly inherit 'foo>' from '+OtherClass'
</code></pre>

<dt><a name="do"><code>(do 'flg|num ['any | (NIL 'any . prg) | (T 'any . prg) ..]) -> any</code></a>
<dd>Counted loop with multiple conditional exits: The body is executed at most
<code>num</code> times (or never (if the first argument is <code>NIL</code>), or
an infinite number of times (if the first argument is <code>T</code>)). If a
clause has <code>NIL</code> or <code>T</code> as its CAR, the clause's second
element is evaluated as a condition and - if the result is <code>NIL</code> or
non-<code>NIL</code>, respectively - the <code>prg</code> is executed and the
result returned. Otherwise (if count drops to zero), the result of the last
expression is returned. See also <code><a href="refL.html#loop">loop</a></code>
and <code><a href="refF.html#for">for</a></code>.

<pre><code>
: (do 4 (printsp 'OK))
OK OK OK OK -> OK
: (do 4 (printsp 'OK) (T (= 3 3) (printsp 'done)))
OK done -> done
</code></pre>

<dt><a name="doc"><code>(doc ['sym1] ['sym2])</code></a>
<dd>Opens a browser, and tries to display the reference documentation for
<code>sym1</code>. <code>sym2</code> may be the name of a browser. If not given,
the value of the environment variable <code>BROWSER</code>, or the
<code>w3m</code> browser is tried. If <code>sym1</code> is <code>NIL</code>, the
<a href="ref.html">PicoLisp Reference</a> manual is opened. See also <a
href="ref.html#fun">Function Reference</a> and <code><a
href="refV.html#vi">vi</a></code>.

<pre><code>
: (doc '+)  # Function reference
-> T
: (doc '+relation)  # Class reference
-> T
: (doc)  # Reference manual
-> T
:  (doc 'vi "firefox")  # Use alternative browser
-> T
</code></pre>

</dl>

</body>
</html>
